Classification and difference of base oils(1)

Base oil types are divided into five categories as follows.

The first category, conventional solvent-refined mineral oils.

The second category, hydrocracked mineral oils.

The third catagory, highly hydrocracked or hydroisomerized waxes.

The fourth category, polyalpha-olefins (PAO).

The fifth category, other synthetic oils

The quality of the base oil produced depends on the content and nature of the ideal components in the raw material. Therefore, this type of base oil is limited in performance.

Type II base oils are produced by a combination of processes (solvent process and hydrogenation process), which are mainly chemical processes not limited by raw materials and can change the original hydrocarbon structure. Therefore, II base oil has less impurities (aromatic content less than 10%), high saturated hydrocarbon content, good thermal stability and oxygen resistance, and better low temperature and soot dispersion performance than I base oil.

Type III base oils are produced by a fully hydrogenated process and are conventional base oils (UCBO) with a high viscosity index compared to Type II base oils. Type III base oils are far superior to Type I and II base oils in terms of performance, especially with a very high viscosity index and low volatility. The performance of some Group III oils is comparable to that of polyalpha-olefins (PAO), and they are much less expensive than synthetic oils. In terms of appearance, the higher the degree of refinement the purer it looks, so Class III is light in color and Class I is dark in color

Synthetic oils include PAO, diesters, polyol esters, polyethers, silicone oils, phosphate esters

PAO has good compatibility with additives, oil seal materials, coatings and mineral oil as a base oil for vehicles, and it is one of the least expensive synthetic oils of all kinds.

Although ester base oil has good resistance to high and low temperature and anti-wear, it is unstable in water, easy to corrode, and has poor compatibility with oil seal and coating, and the cost is not low, so there is no such commodity production nowadays. Polyether is slightly better than esters for water and oil, but it is not easy to be compatible with mineral oil and additives, and the price is high, so it cannot be widely used.

Lubricants made from polyalpha-olefins (PAO) as base oils have many advantages over petroleum-based mineral oil lubricants. The first is that the thermal oxidation stability of PAO oils is significantly better than that of mineral oils. When subjected to a 165°C, 5-day hot oil oxidation test, the 40°C viscosity of petroleum-based oils was reduced from 95mm2/s increased to 146.3mm2 /s and Viscosity change rate is 54.0 percent. And PAO type synthetic lubricant viscosity only changed from 94.0mm2/s to 96.8 mm2/s and The viscosity change rate is only 3 percent. 

This means that the use of PAO synthetic lubricants can extend oil change intervals, which means less downtime and lower maintenance costs. On the other hand, it also shows that the use of PAO base oils can be used with fewer additives or less expensive additives. This can reduce PAO based synthetic lubricants, making them more competitive with petroleum-based lubricants. So what are the actual brands of oils on the market?